ShrewSoft IKE Client and the patch for kernels 6.10 or posterior

 Compile this:

https://github.com/dolomighty/shrewsoft-ike

And apply this patch for kernels after 6.10

https://aur.archlinux.org/cgit/aur.git/tree/deprecating_udp_encap_espinudp_non_ike.patch?h=ike

when failing the GUI because of the upgrade to qt6, you can run ikec with

qikec -r RENTAS -u YOUR_USER -p 'YOUR_PASSWORD' -a

Configure iked as a service:

create the file 

/etc/systemd/system/iked.service

with the content

[Unit]

Description=Shrew Soft IKE Daemon

After=network-online.target

Wants=network-online.target

[Service]

Type=simple

ExecStart=/usr/sbin/iked -F

Restart=on-failure

[Install]

WantedBy=multi-user.target

then run:

sudo systemctl daemon-reload

sudo systemctl enable iked

sudo systemctl start iked